The present invention relates to a charged particle beam apparatus.
In manufacturing process of semiconductor devices and magnetic disks, a charged particle beam measuring device to measure the shape and size of a pattern formed on a sample, and a charged particle beam inspecting device to examine presence/absence of defect, are used. These devices irradiate the sample with a charged particle beam (hereinbelow, a primary beam) such as an electronic beam or ion beam and acquire a secondary charged particle signal such as secondary electrons caused by the irradiation. As such charged particle beam device, a scanning electron microscope (SEM) device has been conventionally used.
In recent years, miniaturization of semiconductor devices is approaching the limit, and as high-integration in place of the miniaturization, three-dimensional device structure is promoted. Upon inspection and measurement of three-dimensional device, it is required to acquire information on the both of the highest part and the lowest part of the uneven sample surface. Accordingly, it is necessary to increase the focus of depth of the SEM. The depth of focus is an allowable range of shift from just focus state upon observation. The blur of electron beam due to focus shift increases in accordance with opening angle of the electron beam on the sample. To increase the depth of focus, it is necessary to reduce the opening angle. However, when the opening angle is reduced, a diffraction aberration, caused by electron wave nature, which becomes smaller in inversely proportional to the opening angle, is increased. Thus there is a physical limitation that the resolution is degraded. That is, the depth of focus and the resolution are in trade-off relationship.
In projection exposure devices, as means for improving the depth of focus, an off-axis-illumination technique of providing an aperture with a light shielding plate on an optical axis of an optical system is proposed. For example, Japanese Unexamined Patent Application Publication No. 2004-63988 shows openings to form various effective light source topographies in addition to an annular aperture and a quadrupole aperture. Further, Japanese Unexamined Patent Application Publication No. 2002-124205 shows, among these off-axis-illuminations, as an application of annular illumination to a charged particle beam device, gathering an electron beam passed through the annular aperture in a probe shape. According to this method, it is possible to provide a scanning charged particle microscope with improved resolution and improved depth of focus.
Further, as a high resolution optical photography, deconvolution is known. The deconvolution is eliminating only beam profile information from an acquired image to sharpen the original image. For example, Japanese Unexamined Patent Application Publication No. 2014-197115 shows homogenizing blur of a dot image with respect to focus shift by, in a pupil plane of an image-sensing camera optical system, applying phase distribution given as a three-dimensional function to pupil plane coordinates, and eliminating the homogeneous blur by deconvolution, to enlarge the depth of field and the depth of focus of the optical system. Note that the annular structure shown in Japanese Unexamined Patent Application Publication No. 2014-197115 corresponds to rotation symmetric phase distribution. It is necessary to pay attention that the annular structure is different from the annular aperture shown in Japanese Unexamined Patent Application Publication Nos. 2004-63988 and 2002-124205. Further, Japanese Unexamined Patent Application Publication No. 2005-302359 shows application of deconvolution to a charged particle beam device.